1. Field of the Invention
This invention relates to fastening devices and more particularly to adjustable reusable bolts for fastening structural parts in firm engagement and in alignment relative to each other.
2. Description of the Prior Art
In assembling structural components in firm engagement, it is frequently necessary to insert a bolt or other fastening device in an opening which is difficult of access and where, for example, the assembly may have to be accomplished using only one hand. For example, in large generators, it is customary to form the end shields in two portions abutting along a horizontal plane. The upper and lower end shield portions are usually formed with inwardly extending flanges forming the abutting surfaces and aligned apertures are provided in the flanges for receiving fastening bolts. Because the flanges extend inwardly, they are accessible only through manholes in the generator casing which frequently allow access to the bolts with only one arm and with the assembler in many cases being unable actually to see the openings into which the bolt is to be assembled.
In prior art structures of this type, it has been considered desirable to employ a bolt which has a body portion having as close a fit as possible with the walls of the apertures in the upper and lower portions of the end shield in which the bolt is to be received. However, because of the difficulty of access, where bolts having the desired close fit have been used, inserting the bolts into the apertures has involved great difficulty. Also, because it is difficult to form the tapped recess into which the threaded portion of the bolt is to be inserted in precise axial alignment with the apertures, it has been found necessary to accept less than a perfect fit between the body portion of the bolt and the walls of the apertures. Thus, in order to insure ability to insert the bolt under the difficult access conditions and with the aforementioned lack of precise axial alignment, it has been found necessary to provide clearance between the body portion and the walls of the apertures. While such clearance facilitates insertion of the bolt, it has permitted some slight misalignment of the vertical faces on the upper and lower portions of the end shield, and even a very small step in these vertical faces resulting from such misalignment can be sufficient to result in leakage of hydrogen which is employed for cooling such large generators.
The prior art discloses fastening devices, including adjustable bushings, for effecting a very tight radial fit with the side walls of an opening in which such fastening devices are received. For example, such devices manufactured by Adjustable Bushing Corporation include alternate male and female tapered rings which expand radially as a longitudinal force is exerted thereon. Such fastening devices may be formed as bolts which extend entirely through aligned openings or may be formed to be received in a blind recess.
In accordance with the present invention, fastening devices of the type referred to in the preceding paragraph have been modified to make them effective for assembling heavy structural members, such as generator end shields or other components, where accessibility is difficult and where assembly and disassembly may have to be effected using only one hand.
It is, therefore, an object of this invention to provide a fastening device which can be employed to effect assembly of structural members where access is limited.
It is another object of this invention to provide such a fastening device which may be placed in assembled position and removed therefrom using only one hand.
It is still a further object of this invention to provide a fastening device which, despite the difficulty of access, enables a firm sealing engagement to be effected between abutting structural members with the use of a minimal number of such fastening devices.
It is another object of this invention to provide a fastening device which automatically effects alignment of heavy structural members which may be slightly out of alignment before the fastening device is placed in assembled position.
It is still another object of this invention to provide a fastening device which facilitates easy assembly under difficult access conditions even though a recess which receives the threaded portion of the fastening device may be out of alignment with an adjacent aperture which receives the body portion of the fastening device.